Quantitative examination of taste buds on the soft palate and the tongue in the rat during the postnatal development revealed that there exist 200 taste buds on the soft palate at birth as many as in 3-week-old although taste pore were observed in 50 taste buds. On the contrary, less than 100 taste buds, without observation of taste pore, existed in fungiform papillae on the anterior tongue in new born rats, and the number of taste buds postnatally increased during 4 weeks, reached to the maximum of 200. Electrophysiological recordings from the GSP in the rat and hamster showed that taste stimulation with sweet substances on the sofr palate produces robust responses on the GSP nerve. The rat GSP produced robust responses not only to sugars but also to various amino acids. In the rat chorda tympani, L-amino acids are more stimulatory than the D-forms, while the GSP responds better to Damino acids compared to the enantiomers. Also, bilateral transection of the GSP and/or CT nerves in the hamster resulted in a significant reduction of the conditioned taste aversion for sucrose. The order of the sectioning effects was GSP + CT > GSP (〕SY.gtoreq.〔) CT > sham. Considering numeral taste buds distributed on the soft palate, and the strong responsiveness for sweet substances including many amino acids, gustatory function of the soft palate should play an important role on the ingestion of milk during early development in postnatal stage.